[Chronic recurrent multifocal osteomyelitis with interstitial myositis]

Chronic recurrent multifocal osteomyelitis (CRMO) is an inflammatory, non-infectious disorder of skeletal system mainly seen in children. We report a case of CRMO presenting with fever and leg pain. The patient was an 11-year-old boy complaining of a fever, swelling and pain on his right foot, and pain on both legs. Although serum levels of CK and aldolase were not increased, MRI imaging suggested polymyositis. Muscle biopsy showed interstitial infiltration of inflammatory cells without any evidences of dermatomyositis or polymyositis. One month later, he complained of a swelling, pain and redness of his left clavicle as recurrently experienced during the recent 6 months, and MRI investigation indicated the diagnosis of osteomyelitis. Bone biopsy was performed and showed chronic inflammatory changes with negative bacterial culture. Multiple bone lesions and muscle uptake of FDG in his legs were revealed by whole body FDG-PET/CT, and he was diagnosed as having CRMO with interstitial myositis. The combinatorial administration of non-steroidal anti-inflammatory drugs and bisphosphonate successfully improved his clinical symptoms and laboratory abnormalities. To our knowledge, there is no report of a patient of CRMO associated with interstitial myositis.